Ion beam mixing induced by electronic energy deposition in Fe-Si multilayers

Abstract

Spectroscopic properties of Ce³⁺ ions in GdAlO₃ crystal are presented. At least three Ce³⁺ nonequivalent centres (multisites) are present in this crystal. Energy transfer from the Ce³⁺ main in the UV emitting centres to the Ce³⁺ green emitting centres is observed. Ce³⁺ fluorescence decays are either fast (1.5–20 ns) or slower due to complicated processes of energy transfer and migration (Ce³⁺)_i → (Gd³⁺)_n-steps → (Ce³⁺)_j (energy transfer through Gd³⁺ sublattice).     

Partial crystallization of an amorphous alloy by electronic energy deposition

The first experimental evidence is reported of crystallization induced in an amorphous alloy by a high density of electronic excitation deposited along the path of swift heavy ions. The formation of nanocrystalline iron boride phases was observed in an amorphous Fe73.5Cu1Nb3Si13.5B9 alloy irradiated at low temperature with 5 GeV Pb ions up to fluences of 1 x 10(11) ions cm-2. No evidence for the formation of the Fe(Si) phase was found. This phenomenon was interpreted in terms of the relaxation of the high level of energy deposited in electronic excitations along the path of Pb ions in the target, which induces extensive stress and strain that could destabilize the amorphous structure.     

MAPLE deposition of biomaterial multilayers

Double layers of polyethylene glycol (PEG) and 3-(3,4-dihydroxyphenyl)-2-methyl-l-alanine (m-DOPA) thin films were obtained by matrix assisted pulsed laser evaporation (MAPLE) technique, by depositing a first layer of m-DOPA on Si substrate and a second layer of PEG on top of it. The films were characterized by low angle X-ray diffraction (LAXRD), X-ray reflectivity (XRR), atomic force microscopy (AFM), and micro-Raman spectroscopy. From these analyses it resulted that PEG was deposited without any relevant damage both in terms of chemical structure and molecular weight. Furthermore, PEG chains were mostly in the extended conformation, although PEG micelles appeared.     

均匀软X射线多层膜制备方法研究

介绍了基于速度调制技术的均匀软X射线多层膜制备方法,并采用该方法在直径为150mm的平面硅基板上制备出Mo/Si多层膜,其中心波长为13.5nm,膜厚空间非均匀性优于1％,较转盘匀速溅射方法制备的多层膜膜厚空间均匀性提高了近6倍。     

均匀软X射线多层膜制备方法研究

 介绍了基于速度调制技术的均匀软X射线多层膜制备方法，并采用该方法在直径为150mm的平面硅基板上制备出Mo/Si多层膜，其中心波长为13.5nm，膜厚空间非均匀性优于1％，较转盘匀速溅射方法制备的多层膜膜厚空间均匀性提高了近6倍。     

Calculated electronic structure of metallic multilayers formed by noble and transition metals

Full-potential Linearized Augmented Plane Wave calculations are performed to investigate the properties of the electronic charge of metallic multilayers formed by non-magnetic and magnetic elements (i.e. Ag, Cu and Fe). The multilayer structure is of the type A_n, A _n B _n or (AB)_n where A, B indicate Ag, Cu and Fe and n is the number of layers of the element A or B. The problem addressed by this study is the transition from the 2D behavior of the isolated monolayer to the 3D bulklike character. Therefore the calculations, carried out at paramagnetic level, illustrate the dependence of the density of states on the multilayer thickness and composition. For the three elements the main feature of the inter-layer coupling is the absence of charge intermixing and hybridization. For structures with a number of layers n? 5 the density of states bandwidth has a decrease, with respect to the bulk value, approximately proportional to the reduced coordination. At the critical thickness n = 5 and above, a noticeable difference exists between the charge in the outer layers, with reduced coordination and bandwidth, and the central layers with a bulklike density of states. Averaging between these contributions leads to the re-installment of bulklike properties. These results are in essential agreement with analytical band theories and quantum mechanical calculations for similar systems and with experiments. Received 3 October 2001     

Structural ripple formation in Ge/Sb multilayers induced by laser irradiation

Thin multilayer films (Ge/Sb/Ge/Sb/Si substrate) have been irradiated with single nanosecond laser pulses (=193 nm). Real-Time Reflectivity (RTR) measurements have been used to follow the transformation in situ and cross-sectional transmission electron microscope analysis was used to study both the microstructure and the composition profile before and after irradiation. Melting and mixing are both found to nucleate at preferential sites in the upper Ge/Sb interface. During this process the film surface topography changes in a way not previously seen, and rippling of the film is observed due to lateral mass flow induced in the Sb layer underneath the surface, most probably arising from volume changes upon melting. For the highest irradiation energy densities, melting of the whole multilayer configuration takes place, the ripples are no longer observed, and following cooling and solidification, a mixed amorphous GeSb film is formed.     

Smoothing of laser energy deposition by gas jets

Smoothing of laser beam non-uniformities using gas jets has been studied. The experiment has been performed with the PALS laser working at 0.44 μm with an intensity of about 10¹⁵ W/cm². The laser beam has been split in two by a prism thus creating an artificial large-scale non-uniformity (≈90 μm). We recorded time resolved and static images of laser-gas jet interaction with and without an Al target. Multi 1D and 2D simulations show that such interaction acts redistributing the over-intensities over larger surface. This effect has to be attributed to ionization processes with consequent laser beam refraction. Results show that Argon gas jet produces a strong refraction of the laser beam thus strongly reducing the initial two spots separation.     

Plasmon energy chemical phase mapping of reactive multilayers

An analytical method of quantitative phase identification and mapping on the nanoscale is presented based on correlative similarity mapping from spectrum images within electron energy loss spectroscopy across the low‐loss plasmon region. The method is applied to map the reaction layer formation for heat treated Cu–Al–Al₂O₃ thin films. Coexistence of residual Al pockets next to polycrystalline but epitaxial CuAl₂ as main reaction product is found as well as a distinctive interfacial plasmon region. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Formation of nickel coatings by electrochemical deposition under X-ray irradiation

The influence of X-ray irradiation on the formation of nickel electroplating coatings is studied. The regularities of the nickel electrocrystallization kinetics under X-ray irradiation of different wavelengths, such as the increase in the deposition rate and metal output by the current, are revealed. The features of the structuring of the nickel electroplating coatings under irradiation are revealed. The influence of X-ray irradiation on microhardness, microdeformations, and dislocation structure is estimated. An increase in microhardness and a decrease in microdeformations of nickel coatings with the growth of the radiation energy are established.     

Pulsed laser deposition of metallic multilayers: the influence of laser power on microstructure

Multilayers of Co and Cu on Si(111) substrates have been produced by pulsed laser deposition at the second harmonic of a Nd:YAG laser (532 nm). The effect of varying the laser power on the film microstructure has been investigated using grazing incidence X-ray reflectivity measurements. Quantitative analysis of the reflectivity curves indicates that higher laser powers are associated with greater intermixing at the Co/Cu interfaces. Offset scans indicate that there is conformal roughness. The deposition process introduces some droplets into the layers, principally of Cu. PACS 61.10Kw; 68.35Ct; 68.65Ac     

Characteristics of ZrC/ZrN and ZrC/TiN multilayers grown by pulsed laser deposition

ZrC/ZrN and ZrC/TiN multilayers were grown on (1 0 0) Si substrates at 300 °C by the pulsed laser deposition (PLD) technique using a KrF excimer laser. X-ray diffraction investigations showed that films were crystalline, the strain and grain size depending on the nature and pressure of the gas used during deposition. The elemental composition, analyzed by Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS), showed that films contained a low level of oxygen contamination. Simulations of the X-ray reflectivity (XRR) curves acquired from films indicated a smooth surface morphology, with roughness below 1 nm (rms) and densities very close to bulk values.Nanoindentation results showed that the ZrC/ZrN and ZrC/TiN multilayer samples exhibited hardness values between 30 and 33 GPa, slightly higher than the values of 28-30 GPa measured for pure ZrC, TiN and ZrN films.     

Charge state dependent energy deposition by ion impact

We report on a measurement of craters in thin dielectric films formed by Xe(Q+) (26 ≤ Q ≤ 44) projectiles. Tunnel junction devices with ion-irradiated barriers were used to amplify the effect of charge-dependent cratering through the exponential dependence of tunneling conductance on barrier thickness. Electrical conductance of a crater σ(c)(Q) increased by 4 orders of magnitude (7.9 × 10(-4) μS to 6.1 μS) as Q increased, corresponding to crater depths ranging from 2 to 11 ?. By employing a heated spike model, we determine that the energy required to produce the craters spans from 8 to 25 keV over the investigated charge states. Considering energy from preequilibrium nuclear and electronic stopping as well as neutralization, we find that at least (27 ± 2)% of available projectile neutralization energy is deposited into the thin film during impact.     

晶粒尺寸对1 MeV电子在金属Ni中能量沉积的影响

采用脉冲电沉积方法制备出高致密、高质量的纳米晶Ni, 并对其密度、组织成分和微观结构进行了表征. 利用高能粒子加速器产生的1 MeV高能电子为辐照源, 研究高能电子在纳米晶Ni和常规粗晶Ni中的能量损失. 通过辐照过程中放置的吸收剂量片来准确表征其电子的能量沉积. 结果表明, 晶粒尺寸对高能电子在材料中的能量沉积有明显的影响, 1 MeV电子在穿过一定厚度的金属Ni后, 在晶粒尺寸细小的纳米晶Ni中测得总的吸收剂量较大, 证明了高能电子在纳米材料中的总能量沉积较小, 从而表现出纳米材料抗辐照的优异性能. 关键词： 高能电子 纳米金属 辐射损伤     

Transonic flow control by means of local energy deposition

Experimental data for the feasibility of transonic flow control by means of energy deposition are generalized. Energy supplied to the immediate vicinity of a body in stream before a compression shock is found to result in the nonlinear interaction of introduced disturbances with the shock and the surface in zones extended along the surface. A new, explosive gasdynamic mechanism behind the shift of the compression shock is discovered. It is shown that the nonlinear character of the interaction may considerably decrease the wave resistance of, e.g., transonic airfoils. It is found that energy supply from without stabilizes a transonic flow about an airfoil—the effect similar to the Khristianovich stabilization effect. The dependence of the energy deposition optimal frequency on the energy source parameters and Mach number of the incoming flow at which the resistance drops to the greatest extent is obtained. The influence of the real thermodynamic properties and viscosity of air is studied.     

Amorphous Si/insulator multilayers grown by vacuum deposition and electron cyclotron resonance plasma treatment

a-Si/insulator multilayers have been deposited on (0 0 1) Si by electron gun Si evaporation and periodic electron cyclotron resonance plasma oxidation or nitridation. Exposure to an O or N plasma resulted in the formation of a thin SiO₂ and SiN_x layer whose thickness was self-limited and controlled by process parameters. For thin-layer (2 nm) Si/SiO₂ and Si/SiN_x multilayers no visible photoluminescence (PL) was observed in most samples, although all exhibited weak “blue” PL. For the nitride multilayers, annealing at 750°C or 850°C induced visible PL that varied in peak energy with Si layer thickness. Depth profiling of a-Si caps on thin insulating layers revealed no detectable contamination for the SiN_x layers, but substantial O contamination for the SiO₂ films.     

Proton irradiation and solid state reaction of Fe−Zr multilayers

The amorphization of Fe−Zr multilayers due to ion-beam mixing and solid state reaction is studied in detail using the CEMS and CXMS. The nature of the amorphous Fe−Zr phase produced by both processes is the same suggesting that diffusion of Fe is an important mechanism during ion-beam mixing.